Such methods of operating a material bed roll mill as well as material bed roll mills themselves are well known in the art and are described in the specialist literature, for example in Walter H. Duda, Cement-Data-Book, Vol. 1, 3rd Edition, 1985, pages 255 to 257.
In the comminution of brittle material for grinding (e.g. cement materials, ore materials, blast furnace slag or the like) is applied, for example with the aid of hydraulic pressure cylinders, to the two grinding rolls which are driven in opposite directions in such a way that the grinding rolls are pressed against one another at high pressure whilst maintaining a variable distance between these two grinding rolls. The material for grinding which is delivered is subjected to material bed comminution in this roll or grinding gap, and the comminuted material leaves this roll gap predominantly in the form of agglomerated scabs which are pressed together and are then broken up or disagglomerated in a separate operation.
In order to determine the output of such material bed roll mills it is also known to use or establish a series of fundamental figures, such as for example the roll diameter, the axial roll length, the circumferential velocity of the rolls, the drive power of the rolls, the grinding force applied to the grinding rolls, the scab thickness (and thus the width of the roll gap between the two grinding rolls) as well as the scab density. Therefore it is usual in the art to use these figures or the values resulting from them for the operation of a material bed roll mill and for control thereof.
However, in practice damage repeatedly occurs on the hard roll surface (roll shell) which can lead to undesirable stoppages of a material bed roll mill.
The object of the invention, therefore, is to provide a method by means of which the material bed roll mill has optimum output and the stoppages which can be attributed to damage to the roll surface can be largely avoided.